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def perm_parity2(a):
   
'''\
    Using algorithm from http://stackoverflow.com/questions/337664/counting-inversions-in-an-array/6424847#6424847
    But substituting Pythons in-built TimSort'''


    a
= list(a)
    b
= sorted(a)
    inversions
= 0
   
while a:
        first
= a.pop(0)
        inversions
+= b.index(first)
        b
.remove(first)
   
return -1 if inversions % 2 else 1

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